PERLINTERN(1) Perl Programmers Reference Guide PERLINTERN(1)
perlintern - autogenerated documentation of purely internal
Perl functions
This file is the autogenerated documentation of functions in
the Perl interpreter that are documented using Perl's inter-
nal documentation format but are not marked as part of the
Perl API. In other words, they are not for use in exten-
sions!
CvWEAKOUTSIDE
Each CV has a pointer, "CvOUTSIDE()", to its lexi-
cally enclosing CV (if any). Because pointers to
anonymous sub prototypes are stored in "&" pad
slots, it is a possible to get a circular reference,
with the parent pointing to the child and
vice-versa. To avoid the ensuing memory leak, we do
not increment the reference count of the CV pointed
to by "CvOUTSIDE" in the one specific instance that
the parent has a "&" pad slot pointing back to us.
In this case, we set the "CvWEAKOUTSIDE" flag in the
child. This allows us to determine under what cir-
cumstances we should decrement the refcount of the
parent when freeing the child.
There is a further complication with non-closure
anonymous subs (i.e. those that do not refer to any
lexicals outside that sub). In this case, the
anonymous prototype is shared rather than being
cloned. This has the consequence that the parent may
be freed while there are still active children, eg
BEGIN { $a = sub { eval '$x' } }
In this case, the BEGIN is freed immediately after
execution since there are no active references to
it: the anon sub prototype has "CvWEAKOUTSIDE" set
since it's not a closure, and $a points to the same
CV, so it doesn't contribute to BEGIN's refcount
either. When $a is executed, the "eval '$x'" causes
the chain of "CvOUTSIDE"s to be followed, and the
freed BEGIN is accessed.
To avoid this, whenever a CV and its associated pad
is freed, any "&" entries in the pad are explicitly
removed from the pad, and if the refcount of the
pointed-to anon sub is still positive, then that
child's "CvOUTSIDE" is set to point to its
grandparent. This will only occur in the single
specific case of a non-closure anon prototype having
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one or more active references (such as $a above).
One other thing to consider is that a CV may be
merely undefined rather than freed, eg "undef &foo".
In this case, its refcount may not have reached
zero, but we still delete its pad and its "CvROOT"
etc. Since various children may still have their
"CvOUTSIDE" pointing at this undefined CV, we keep
its own "CvOUTSIDE" for the time being, so that the
chain of lexical scopes is unbroken. For example,
the following should print 123:
my $x = 123;
sub tmp { sub { eval '$x' } }
my $a = tmp();
undef &tmp;
print $a->();
bool CvWEAKOUTSIDE(CV *cv)
Functions in file pad.h
CX_CURPAD_SAVE
Save the current pad in the given context block
structure.
void CX_CURPAD_SAVE(struct context)
CX_CURPAD_SV
Access the SV at offset po in the saved current pad
in the given context block structure (can be used as
an lvalue).
SV * CX_CURPAD_SV(struct context, PADOFFSET po)
PAD_BASE_SV
Get the value from slot "po" in the base (DEPTH=1)
pad of a padlist
SV * PAD_BASE_SV(PADLIST padlist, PADOFFSET po)
PAD_CLONE_VARS
|CLONE_PARAMS* param Clone the state variables asso-
ciated with running and compiling pads.
void PAD_CLONE_VARS(PerlInterpreter *proto_perl \)
PAD_COMPNAME_FLAGS
Return the flags for the current compiling pad name
at offset "po". Assumes a valid slot entry.
U32 PAD_COMPNAME_FLAGS(PADOFFSET po)
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PAD_COMPNAME_GEN
The generation number of the name at offset "po" in
the current compiling pad (lvalue). Note that
"SvCUR" is hijacked for this purpose.
STRLEN PAD_COMPNAME_GEN(PADOFFSET po)
PAD_COMPNAME_GEN_set
Sets the generation number of the name at offset
"po" in the current ling pad (lvalue) to "gen".
Note that "SvCUR_set" is hijacked for this purpose.
STRLEN PAD_COMPNAME_GEN_set(PADOFFSET po, int gen)
PAD_COMPNAME_OURSTASH
Return the stash associated with an "our" variable.
Assumes the slot entry is a valid "our" lexical.
HV * PAD_COMPNAME_OURSTASH(PADOFFSET po)
PAD_COMPNAME_PV
Return the name of the current compiling pad name at
offset "po". Assumes a valid slot entry.
char * PAD_COMPNAME_PV(PADOFFSET po)
PAD_COMPNAME_TYPE
Return the type (stash) of the current compiling pad
name at offset "po". Must be a valid name. Returns
null if not typed.
HV * PAD_COMPNAME_TYPE(PADOFFSET po)
PAD_DUP Clone a padlist.
void PAD_DUP(PADLIST dstpad, PADLIST srcpad, CLONE_PARAMS* param)
PAD_RESTORE_LOCAL
Restore the old pad saved into the local variable
opad by PAD_SAVE_LOCAL()
void PAD_RESTORE_LOCAL(PAD *opad)
PAD_SAVE_LOCAL
Save the current pad to the local variable opad,
then make the current pad equal to npad
void PAD_SAVE_LOCAL(PAD *opad, PAD *npad)
PAD_SAVE_SETNULLPAD
Save the current pad then set it to null.
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void PAD_SAVE_SETNULLPAD()
PAD_SETSV
Set the slot at offset "po" in the current pad to
"sv"
SV * PAD_SETSV(PADOFFSET po, SV* sv)
PAD_SET_CUR
Set the current pad to be pad "n" in the padlist,
saving the previous current pad. NB currently this
macro expands to a string too long for some com-
pilers, so it's best to replace it with
SAVECOMPPAD();
PAD_SET_CUR_NOSAVE(padlist,n);
void PAD_SET_CUR(PADLIST padlist, I32 n)
PAD_SET_CUR_NOSAVE
like PAD_SET_CUR, but without the save
void PAD_SET_CUR_NOSAVE(PADLIST padlist, I32 n)
PAD_SV Get the value at offset "po" in the current pad
void PAD_SV(PADOFFSET po)
PAD_SVl Lightweight and lvalue version of "PAD_SV". Get or
set the value at offset "po" in the current pad.
Unlike "PAD_SV", does not print diagnostics with
-DX. For internal use only.
SV * PAD_SVl(PADOFFSET po)
SAVECLEARSV
Clear the pointed to pad value on scope exit. (i.e.
the runtime action of 'my')
void SAVECLEARSV(SV **svp)
SAVECOMPPAD
save PL_comppad and PL_curpad
void SAVECOMPPAD()
SAVEPADSV
Save a pad slot (used to restore after an iteration)
XXX DAPM it would make more sense to make the arg a
PADOFFSET void SAVEPADSV(PADOFFSET po)
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Functions in file pp_ctl.c
find_runcv
Locate the CV corresponding to the currently execut-
ing sub or eval. If db_seqp is non_null, skip CVs
that are in the DB package and populate *db_seqp
with the cop sequence number at the point that the
DB:: code was entered. (allows debuggers to eval in
the scope of the breakpoint rather than in the scope
of the debugger itself).
CV* find_runcv(U32 *db_seqp)
PL_DBsingle
When Perl is run in debugging mode, with the -d
switch, this SV is a boolean which indicates whether
subs are being single-stepped. Single-stepping is
automatically turned on after every step. This is
the C variable which corresponds to Perl's
$DB::single variable. See "PL_DBsub".
SV * PL_DBsingle
PL_DBsub
When Perl is run in debugging mode, with the -d
switch, this GV contains the SV which holds the name
of the sub being debugged. This is the C variable
which corresponds to Perl's $DB::sub variable. See
"PL_DBsingle".
GV * PL_DBsub
PL_DBtrace
Trace variable used when Perl is run in debugging
mode, with the -d switch. This is the C variable
which corresponds to Perl's $DB::trace variable.
See "PL_DBsingle".
SV * PL_DBtrace
PL_dowarn
The C variable which corresponds to Perl's $^W warn-
ing variable.
bool PL_dowarn
PL_last_in_gv
The GV which was last used for a filehandle input
operation. ("<FH>")
GV* PL_last_in_gv
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PL_ofs_sv
The output field separator - $, in Perl space.
SV* PL_ofs_sv
PL_rs The input record separator - $/ in Perl space.
SV* PL_rs
is_gv_magical
Returns "TRUE" if given the name of a magical GV.
Currently only useful internally when determining if
a GV should be created even in rvalue contexts.
"flags" is not used at present but available for
future extension to allow selecting particular
classes of magical variable.
Currently assumes that "name" is NUL terminated (as
well as len being valid). This assumption is met by
all callers within the perl core, which all pass
pointers returned by SvPV.
bool is_gv_magical(char *name, STRLEN len, U32 flags)
start_glob
Function called by "do_readline" to spawn a glob (or
do the glob inside perl on VMS). This code used to
be inline, but now perl uses "File::Glob" this glob
starter is only used by miniperl during the build
process. Moving it away shrinks pp_hot.c; shrinking
pp_hot.c helps speed perl up.
PerlIO* start_glob(SV* pattern, IO *io)
CvPADLIST
CV's can have CvPADLIST(cv) set to point to an AV.
For these purposes "forms" are a kind-of CV, eval""s
are too (except they're not callable at will and are
always thrown away after the eval"" is done execut-
ing).
XSUBs don't have CvPADLIST set - dXSTARG fetches
values from PL_curpad, but that is really the call-
ers pad (a slot of which is allocated by every
entersub).
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The CvPADLIST AV has does not have AvREAL set, so
REFCNT of component items is managed "manual"
(mostly in pad.c) rather than normal av.c rules. The
items in the AV are not SVs as for a normal AV, but
other AVs:
0'th Entry of the CvPADLIST is an AV which
represents the "names" or rather the "static type
information" for lexicals.
The CvDEPTH'th entry of CvPADLIST AV is an AV which
is the stack frame at that depth of recursion into
the CV. The 0'th slot of a frame AV is an AV which
is @_. other entries are storage for variables and
op targets.
During compilation: "PL_comppad_name" is set to the
names AV. "PL_comppad" is set to the frame AV for
the frame CvDEPTH == 1. "PL_curpad" is set to the
body of the frame AV (i.e. AvARRAY(PL_comppad)).
During execution, "PL_comppad" and "PL_curpad" refer
to the live frame of the currently executing sub.
Iterating over the names AV iterates over all possi-
ble pad items. Pad slots that are SVs_PADTMP
(targets/GVs/constants) end up having &PL_sv_undef
"names" (see pad_alloc()).
Only my/our variable (SVs_PADMY/SVs_PADOUR) slots
get valid names. The rest are op
targets/GVs/constants which are statically allocated
or resolved at compile time. These don't have names
by which they can be looked up from Perl code at run
time through eval"" like my/our variables can be.
Since they can't be looked up by "name" but only by
their index allocated at compile time (which is usu-
ally in PL_op->op_targ), wasting a name SV for them
doesn't make sense.
The SVs in the names AV have their PV being the name
of the variable. NV+1..IV inclusive is a range of
cop_seq numbers for which the name is valid. For
typed lexicals name SV is SVt_PVMG and SvSTASH
points at the type. For "our" lexicals, the type is
SVt_PVGV, and GvSTASH points at the stash of the
associated global (so that duplicate "our" declara-
tions in the same package can be detected). SvCUR
is sometimes hijacked to store the generation number
during compilation.
If SvFAKE is set on the name SV then slot in the
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frame AVs are a REFCNT'ed references to a lexical
from "outside". In this case, the name SV does not
have a cop_seq range, since it is in scope
throughout.
If the 'name' is '&' the corresponding entry in
frame AV is a CV representing a possible closure.
(SvFAKE and name of '&' is not a meaningful combina-
tion currently but could become so if "my sub foo
{}" is implemented.)
The flag SVf_PADSTALE is cleared on lexicals each
time the my() is executed, and set on scope exit.
This allows the 'Variable $x is not available' warn-
ing to be generated in evals, such as
{ my $x = 1; sub f { eval '$x'} } f();
AV * CvPADLIST(CV *cv)
cv_clone
Clone a CV: make a new CV which points to the same
code etc, but which has a newly-created pad built by
copying the prototype pad and capturing any outer
lexicals.
CV* cv_clone(CV* proto)
cv_dump dump the contents of a CV
void cv_dump(const CV *cv, const char *title)
do_dump_pad
Dump the contents of a padlist
void do_dump_pad(I32 level, PerlIO *file, PADLIST *padlist, int full)
intro_my
"Introduce" my variables to visible status.
U32 intro_my()
pad_add_anon
Add an anon code entry to the current compiling pad
PADOFFSET pad_add_anon(SV* sv, OPCODE op_type)
pad_add_name
Create a new name in the current pad at the speci-
fied offset. If "typestash" is valid, the name is
for a typed lexical; set the name's stash to that
value. If "ourstash" is valid, it's an our lexical,
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set the name's GvSTASH to that value
Also, if the name is @.. or %.., create a new array
or hash for that slot
If fake, it means we're cloning an existing entry
PADOFFSET pad_add_name(char *name, HV* typestash, HV* ourstash, bool clone)
pad_alloc
Allocate a new my or tmp pad entry. For a my, simply
push a null SV onto the end of PL_comppad, but for a
tmp, scan the pad from PL_padix upwards for a slot
which has no name and no active value.
PADOFFSET pad_alloc(I32 optype, U32 tmptype)
pad_block_start
Update the pad compilation state variables on entry
to a new block
void pad_block_start(int full)
pad_check_dup
Check for duplicate declarations: report any of:
* a my in the current scope with the same name;
* an our (anywhere in the pad) with the same
name and the same stash
as "ourstash" "is_our" indicates that the
name to check is an 'our' declaration
void pad_check_dup(char* name, bool is_our, HV* ourstash)
pad_findlex
Find a named lexical anywhere in a chain of nested
pads. Add fake entries in the inner pads if it's
found in an outer one. innercv is the CV *inside*
the chain of outer CVs to be searched. If newoff is
non-null, this is a run-time cloning: don't add fake
entries, just find the lexical and add a ref to it
at newoff in the current pad.
PADOFFSET pad_findlex(const char* name, PADOFFSET newoff, const CV* innercv)
pad_findmy
Given a lexical name, try to find its offset, first
in the current pad, or failing that, in the pads of
any lexically enclosing subs (including the compli-
cations introduced by eval). If the name is found in
an outer pad, then a fake entry is added to the
current pad. Returns the offset in the current pad,
or NOT_IN_PAD on failure.
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PADOFFSET pad_findmy(char* name)
pad_fixup_inner_anons
For any anon CVs in the pad, change CvOUTSIDE of
that CV from old_cv to new_cv if necessary. Needed
when a newly-compiled CV has to be moved to a pre-
existing CV struct.
void pad_fixup_inner_anons(PADLIST *padlist, CV *old_cv, CV *new_cv)
pad_free
Free the SV at offset po in the current pad.
void pad_free(PADOFFSET po)
pad_leavemy
Cleanup at end of scope during compilation: set the
max seq number for lexicals in this scope and warn
of any lexicals that never got introduced.
void pad_leavemy()
pad_new Create a new compiling padlist, saving and updating
the various global vars at the same time as creating
the pad itself. The following flags can be OR'ed
together:
padnew_CLONE this pad is for a cloned CV
padnew_SAVE save old globals
padnew_SAVESUB also save extra stuff for start of sub
PADLIST* pad_new(int flags)
pad_push
Push a new pad frame onto the padlist, unless
there's already a pad at this depth, in which case
don't bother creating a new one. If has_args is
true, give the new pad an @_ in slot zero.
void pad_push(PADLIST *padlist, int depth, int has_args)
pad_reset
Mark all the current temporaries for reuse
void pad_reset()
pad_setsv
Set the entry at offset po in the current pad to sv.
Use the macro PAD_SETSV() rather than calling this
function directly.
void pad_setsv(PADOFFSET po, SV* sv)
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pad_swipe
Abandon the tmp in the current pad at offset po and
replace with a new one.
void pad_swipe(PADOFFSET po, bool refadjust)
pad_tidy
Tidy up a pad after we've finished compiling it:
* remove most stuff from the pads of anonsub
prototypes;
* give it a @_;
* mark tmps as such.
void pad_tidy(padtidy_type type)
pad_undef
Free the padlist associated with a CV. If parts of
it happen to be current, we null the relevant
PL_*pad* global vars so that we don't have any dan-
gling references left. We also repoint the CvOUTSIDE
of any about-to-be-orphaned inner subs to the outer
of this cv.
(This function should really be called pad_free, but
the name was already taken)
void pad_undef(CV* cv)
djSP Declare Just "SP". This is actually identical to
"dSP", and declares a local copy of perl's stack
pointer, available via the "SP" macro. See "SP".
(Available for backward source code compatibility
with the old (Perl 5.005) thread model.)
djSP;
LVRET True if this op will be the return value of an
lvalue subroutine
report_uninit
Print appropriate "Use of uninitialized variable"
warning
void report_uninit()
sv_add_arena
Given a chunk of memory, link it to the head of the
list of arenas, and split it into a list of free
SVs.
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void sv_add_arena(char* ptr, U32 size, U32 flags)
sv_clean_all
Decrement the refcnt of each remaining SV, possibly
triggering a cleanup. This function may have to be
called multiple times to free SVs which are in com-
plex self-referential hierarchies.
I32 sv_clean_all()
sv_clean_objs
Attempt to destroy all objects not yet freed
void sv_clean_objs()
sv_free_arenas
Deallocate the memory used by all arenas. Note that
all the individual SV heads and bodies within the
arenas must already have been freed.
void sv_free_arenas()
The autodocumentation system was originally added to the
Perl core by Benjamin Stuhl. Documentation is by whoever was
kind enough to document their functions.
perlguts(1), perlapi(1)
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